In the sawing of pipes and similar hollow generally cylindrical objects made of materials such as asbestos-cement or concrete, considerable amounts of sawdust are generated both outside and inside the pipe. The dust generated outside the pipe surface represents a particularly serious problem, for such airborne dust can be respired by the saw operator and others in the immediate vicinity of the cutting operation. The airborne dust can also settle on nearby equipment, requiring frequent cleaning of the equipment and posing the problem of undue wear and mechanical failure of the equipment if the dust works into equipment components such as bearings, gear trains and the like. The dust generated inside the hollow pipe or similar object is a lesser problem because it is to some extent contained within the walls of the pipe. It is still of concern, however, because when the cut pieces of pipe are separated the dust inside frequently becomes airborne and is thus detrimental for the reasons just described. Similarly, during the cutting operation some of the dust generated inside the pipe can sift out through the saw kerf and become airborne. Containment of dust within the pipe body is also quite limited when the cutting operation takes place near the open end of the length of pipe.
The problems of dust collection are particularly acute when the saw used to cut the pipe or similar object is a portable circular saw. A fixed saw such as a radial arm saw or a table saw can be completely enclosed by dust collection means such as a housing surrounding the entire device. The portable circular saw, however, is normally used on worksites at locations where construction or use of a dust collection housing enclosing the entire operation is not feasible. Consequently, the problems associated with collecting dust generated by use of a portable circular saw to cut pipe are significantly more severe than the problems associated with dust collection from fixed types of saws.
It would therefore be desirable to have dust collection means capable of being used with portable circular saws and adapted to collect substantially all the dust generated during cutting of pipe or similar hollow generally cylindrical objects with such saws. It would be particularly desirable to have collection means which will collect all the dust generated outside the surface of the pipe, and it would be of added benefit to have apparatus capable of collecting not only the dust generated outside the pipe but also that generated within the hollow interior of the pipe.